UM INFIXATION AND PREFIXATION IN TOBA-BATAK

This report examines the behavior of a morpheme um in Toba Batak (Mala yo-Polynesian) which alternates as a prefix or an infix, and argues th at the observed variation is conditioned by constraints on consonant c lusters. Thus, Toba Batak shows that segmental factors may crucially i nfluence the linear position of affixes, in contrast with a wealth of cases cited in the prosodic morphology literature in support of claims that the distributional properties of morphemes are often conditioned by prosodic structure. In addition, evidence from several sources on Toba Batak suggest that um in this language has been mi,orating from i nfixed to prefixed positions over time, and that taken as a whole, the stages involved in this change are linguistically coherent. This patt ern of shift has interesting implications for typology and for theorie s of language evolution.